Correcting typewriters have long been known (e.g., patent No. 3,780,846 entitled "Automatic Erasing Typewriter" and filed by Robert A. Kolpek et al, which issued Oct. 9, 1973) which can remove incorrect characters and allow entry of correct ones by following an appropriate sequence of keystrokes. For example, backspacing to the end of an incorrect word, selecting an "erase only" mode if characters erased from a document are to be retyped subsequently, changing to an "erase and delete" mode where new characters are to be entered by the typist in place of one or more erroneous characters, and pressing a "retype" key when erased material stored in memory is to be recalled and reprinted.
In recent years, "Dictionary" typewriters have appeared on the market which contain a listing of over 50,000, say, correctly-spelled words stored in a read-only section of an electronic memory. An error detection unit monitors successive text entries and emits a visual or auditory signal when comparison of an entered word with the words in the "dictionary" shows disagreement with spelling of the entered word. The signal is an indication that spelling of the last-entered word should at least be checked in a printed dictionary. In more powerful versions where the typewriter has an associated display unit, the typist may then enter those initial letters of the incorrect word believed correct and cause a search of the dictionary to find successive, alphabetically-ordered "trial" words sharing the initial letters of the incorrect word (a "List Mode" as it has been termed), one of these trial words then being chosen to replace the incorrect word.
Recently, the market has likewise seen the advent of electronic typewriters with memories storing thesauri from which one can retrieve a succession of synonyms for replacement of an undesired word. Here too, correction of printed text has involved the typist's initiation of two or more steps to effect the desired result.
While the foregoing improvements have done much to enhance the quality of communications prepared by poor spellers, dull writers, etc., the efficiency of typewriter or word-processor use is still susceptible of further increase because of unproductive time associated with interaction between the typist and the text display--e.g. moving a type carrier (and/or cursor, if a display is used), selecting particular corrective modes while moving to a desired spot in the text and selecting other corrective modes at that spot, etc., after detecting the undesired word. This last may be an erroneous word with a typographical or other error in it or it may simply be a trite word.
Thus, printed text requiring replacement of one word by another should be revisable in a simple, fully automatic operation, ending with properly aligned text once again. Preferably, this occurs upon depression of just one key.